MBT Men's Grey Sport2 Athletic Walking Shoes Lightweight 3D mesh upper and lining are highly breathable PU coated materials are durable and resistant Dual density midsole is made with TPU and nylon mixed with glass fibers for extra firmness and durability Multi-layered sole creates natural instability to emulate the feeling of walking on sand, and allows for better posture, toning properties, alleviation of back and foot pain, and increases shock absorption Durable rubber outsole provides excellent traction